A voltage sampling circuit may be used to sample a voltage at different points in time. However a problem arises when voltage transients are produced due to inductance of the conductor which provides the voltage to the voltage sampling circuit. These voltage transients may cause the voltage sampling circuit to incorrectly measure the voltage being provided. That is, the voltage to be measured may be different than the voltage that is provided at the input of the voltage sampling circuit due to the inductance of the conductor. The problem of voltage transients may be even more of a problem at higher sampling frequencies of the voltage sampling circuit. For example, as clock frequencies in integrated circuits increase and the sample time decreases, voltage transients will cause more of a problem in accurately sampling voltage values.
Referring to prior art FIG. 1, a portion of a sigma-delta converter integrated circuit 12 is illustrated. Note that voltage sampling circuit 16 uses two inverted, non-overlapping clocks where the active phase P1 of the first clock closes switches 34 and 35 and the active phase P2 of the second clock closes switches 30 and 31. The large external filter capacitor 22 is used to filter noise from positive bandgap reference voltage VREFP and from negative bandgap reference voltage VREFN. Filter capacitor 22 is also used to provide a low source impedance to voltage sampling circuit 16. When voltage sampling circuit 16 samples the voltages at nodes N3 and N4, a relatively large current flows through bond wires 18 and 19 as capacitors 24 and 26 initially charge. The large initial current flow will cause voltage transients across bond wires 18 and 19. If the sampling frequency of voltage sampling circuit 16 is slow enough, the voltage transients across bond wires 18 and 19 will decay before the end of the sampling period. However, if the sampling frequency is high enough so that the voltage transients do not subside to a sufficient level before the end of the sampling period, then a voltage error will be sampled at nodes N3 and N4.